1. Field of the Invention
The present invention relates to a display and a method of controlling the same, and more particularly, it relates to a display having a memory in a pixel part and a method of controlling the same.
2. Description of the Background Art
Demand for a miniature liquid crystal display (LCD) employing polysilicon TFTs (thin-film transistors) is recently increased. Therefore, power consumption in a display system including a liquid crystal panel and an external control IC must be reduced. Particularly in a liquid crystal display carried on a portable telephone driven by a cell, power consumption must be reduced. Therefore, the liquid crystal display employed for the portable telephone must also be reduced in power consumption, particularly in a wait screen in a wait state.
In order to reduce power consumption in the wait screen of the liquid crystal display carried on the potable screen, various technical developments are made by turning off a backlight, employing a partial display system of displaying necessary information only on part of the LCD screen etc.
In order to reduce power consumption in the wait screen, an LCD having a built-in memory is proposed as a system storing a memory such as an SRAM (static random access memory) in a pixel part of the LCD while stopping driving by a peripheral circuit in a wait state thereby implementing low power consumption.
The LCD having a built-in memory includes three operation modes, i.e., an operation mode in general application, an operation mode for writing video data to be displayed in a wait state and an operation mode in a standby state. In the general application, the LCD operates on the basis of basic clocks consisting of horizontal and vertical clocks. In other words, the LCD writes video data in pixels through a data line driving circuit and a scanning line driving circuit arranged around the pixels in the general application operation mode.
In the operation mode for writing the video data to be displayed in the wait state, the LCD writes the video data in the memory before making transition to the standby state. In the operation mode in the standby state, the LCD writes video data to be displayed in the standby state from the memory in the liquid crystals.
The aforementioned conventional LCD having a built-in memory (SRAM) writes the video data in the memory when making transition to the standby state, and hence the memory is activated in the wait state and the standby state and inactivated in the general application. When a power supply circuit for driving the memory is started when the memory makes transition from the inactive state for general application to an active state in the standby state in this case, a through current flows to the memory (SRAM), to disadvantageously increase current consumption.
When starting of the power supply circuit for driving the memory and data writing are simultaneously performed when the memory makes transition from the inactive state for general application to the active state in the standby state, it is disadvantageously difficult to write data due to the through current of the aforementioned memory (SRAM).